Fuzzer failure: JIT un-opt eval mismatch vs. all other eval, interpreter un-opt included

[angelomatni1]

Repro:

bazel test -c opt //xls/fuzzer:run_crasher_test_2026-05-12_dad0

Error:

evaluated opt IR (JIT), evaluated opt IR (interpreter), evaluated unopt IR (interpreter), interpreted DSLX =
   (bits[11]:0x2ab, bits[48]:0x7fff_ffff_ffff, (), bits[48]:0xffff_ffff_faab, bits[8]:0xff, bits[48]:0xffff_ffff_ffff)
evaluated unopt IR (JIT) =
   (bits[11]:0x7ab, bits[48]:0x7fff_ffff_ffff, (), bits[48]:0xffff_ffff_ffab, bits[8]:0xff, bits[48]:0xffff_ffff_ffff)

[angelomatni1]

A minimized IR with the interpreter vs LLVM JIT error:

Input:

bits[29]:0x1555_5555; [[bits[52]:0x0, bits[52]:0x9_6fca_a704_5238, bits[52]:0x8_8a89_be10_6aaa, bits[52]:0xa_aaaa_aadf_fbff, bits[52]:0x3_a92a_2ace_0501, bits[52]:0xa_aaaa_aaaa_aaaa, bits[52]:0xc_2aac_e82b_bbbf, bits[52]:0xd_c2e4_5e82_99f9], [bits[52]:0x8000, bits[52]:0x8_361f_c066_8cfa, bits[52]:0xa_a8aa_aadc_fddd, bits[52]:0xa_aaaa_aad5_5555, bits[52]:0x2_e392_3b32_feed, bits[52]:0x8_aa0a_80ee_8e2a, bits[52]:0xa_aaaa_aaaa_aaaa, bits[52]:0x0], [bits[52]:0x7_ffff_ffff_ffff, bits[52]:0x5_5555_5555_5555, bits[52]:0x8, bits[52]:0xa_aaaa_aaaa_aaaa, bits[52]:0xa_aaaa_aaaa_aaaa, bits[52]:0xa_a622_813c_0000, bits[52]:0x1_56f0_78ff_2778, bits[52]:0x7_ffff_ffff_ffff], [bits[52]:0x7_ffff_ffff_ffff, bits[52]:0x6_2a37_d3bc_cff1, bits[52]:0xa_aaaa_aaa0_0400, bits[52]:0x2_0000, bits[52]:0xa_e87a_79cf_aeb8, bits[52]:0x0, bits[52]:0x1_a384_abd3_94f4, bits[52]:0x5_5555_5555_5555], [bits[52]:0x20, bits[52]:0x7_ffff_ffff_ffff, bits[52]:0x7_ffff_ffff_ffff, bits[52]:0x7_ffff_ffff_ffff, bits[52]:0xaa49_ab30_367c, bits[52]:0xa_aaaa_aae3_aaa6, bits[52]:0x7_ffff_ffff_ffff, bits[52]:0xa_aaaa_aaaa_aaaa], [bits[52]:0x10_0000_0000, bits[52]:0xb_c25a_1034_1eeb, bits[52]:0xb_aaaa_aaa0_8000, bits[52]:0xa_aaaa_aa2c_9d4e, bits[52]:0x5_a716_5baa_bee8, bits[52]:0x4_93aa_88aa_dabe, bits[52]:0x0, bits[52]:0xb_e1ae_ef9e_8663], [bits[52]:0x0, bits[52]:0xe_a8aa_aaab_aaea, bits[52]:0x2_403e_7a69_e927, bits[52]:0xa_aaaa_ea8a_aaaa, bits[52]:0x9_640e_de61_0000, bits[52]:0xa_a8aa_fab8_aba8, bits[52]:0x200, bits[52]:0xa_ae2a_aaf9_ffef], [bits[52]:0x7_ffff_ffff_ffff, bits[52]:0xa_2aaa_aa00_8a0a, bits[52]:0xa22a_ebed_3fbc, bits[52]:0x2_edd6_a1e0_3245, bits[52]:0x0, bits[52]:0x200_0000_0000, bits[52]:0xf_ffff_ffff_ffff, bits[52]:0xf_ffff_ffff_ffff], [bits[52]:0xa_aaaa_aaaa_aaaa, bits[52]:0xe_aa9a_b800_0414, bits[52]:0xf_ffff_ffff_ffff, bits[52]:0xa_aea2_aadd_5717, bits[52]:0xa_aaaa_aaaa_aaaa, bits[52]:0xa_aaa2_afd0_f547, bits[52]:0x2000_0000_0000, bits[52]:0x2_0aba_fd84_6079], [bits[52]:0xe_3886_938a_649c, bits[52]:0xa_aaac_aaaf_daf5, bits[52]:0xa_98be_2fbd_af9d, bits[52]:0x1000_0000_0000, bits[52]:0x2_38b9_ba82_9118, bits[52]:0x7_ffff_ffff_ffff, bits[52]:0x5_5555_5555_5555, bits[52]:0x100], [bits[52]:0x2_0fe1_f9ee_b401, bits[52]:0xa_aaaa_aaaa_aaaa, bits[52]:0x8_a60a_ab81_9788, bits[52]:0xb_2aba_aa08_4810, bits[52]:0xa_9bb5_bc8b_bf0b, bits[52]:0x8_aaa9_aaaf_efff, bits[52]:0x10_0000, bits[52]:0xa_aaaa_aaf5_5775], [bits[52]:0xa_aaaa_aad5_5555, bits[52]:0x1_42b4_dce1_0c7f, bits[52]:0x6_73d5_fcce_b35e, bits[52]:0xa_16b9_ef34_0ce3, bits[52]:0x7_ffff_ffff_ffff, bits[52]:0x8_aaaa_aaaa_aaaa, bits[52]:0xf_ffff_ffff_ffff, bits[52]:0xe_e0a0_0a9e_cea4], [bits[52]:0x7_ffff_ffff_ffff, bits[52]:0xe_bfda_a9d6_cdf6, bits[52]:0xf_ffff_ffff_ffff, bits[52]:0x6e0e_bb69_892c, bits[52]:0x8_aaa0_eb97_440c, bits[52]:0x40_0000_0000, bits[52]:0x0, bits[52]:0xf_aafa_bf80_1328]]; bits[8]:0xff

IR:

package crasher_dad0

file_number 0 "/tmp/crasher_dad0.x"

top fn __crasher_dad0__main(x2: bits[29] id=1, x3: bits[52][8][13] id=2, x4: bits[8] id=3) -> bits[48] {
  concat.12: bits[16] = concat(x4, x4, id=12, pos=[(0,187,22)])
  zero_ext.33: bits[24] = zero_ext(concat.12, new_bit_count=24, id=33, pos=[(0,187,22)])
  concat.14: bits[32] = concat(zero_ext.33, x4, id=14, pos=[(0,187,22)])
  zero_ext.45: bits[40] = zero_ext(concat.14, new_bit_count=40, id=45, pos=[(0,187,22)])
  x8: bits[48] = concat(zero_ext.45, x4, id=16, pos=[(0,187,22)])
  sign_ext.17: bits[29] = sign_ext(x4, new_bit_count=29, id=17)
  x11: bits[2048] = decode(x8, width=2048, id=19, pos=[(0,189,34)])
  x9: bits[29] = smul(sign_ext.17, x2, id=18, pos=[(0,188,22)])
  x17: bits[250] = bit_slice(x11, start=0, width=250, id=23, pos=[(0,191,30)])
  x15: bits[11] = bit_slice(x9, start=0, width=11, id=55, pos=[(0,190,34)])
  ret x23: bits[48] = bit_slice_update(x8, x17, x15, id=32, pos=[(0,197,39)])
}

Mismatch:

JIT: bits[48]:0xffff_ffab
interpreter: bits[48]:0xffff_faab

[angelomatni1]

This is likely an LLVM optimization issue:

INPUT_ARGS='bits[29]:0x1555_5555; [[bits[52]:0x0, bits[52]:0x9_6fca_a704_5238, bits[52]:0x8_8a89_be10_6aaa, bits[52]:0xa_aaaa_aadf_fbff, bits[52]:0x3_a92a_2ace_0501, bits[52]:0xa_aaaa_aaaa_aaaa, bits[52]:0xc_2aac_e82b_bbbf, bits[52]:0xd_c2e4_5e82_99f9], [bits[52]:0x8000, bits[52]:0x8_361f_c066_8cfa, bits[52]:0xa_a8aa_aadc_fddd, bits[52]:0xa_aaaa_aad5_5555, bits[52]:0x2_e392_3b32_feed, bits[52]:0x8_aa0a_80ee_8e2a, bits[52]:0xa_aaaa_aaaa_aaaa, bits[52]:0x0], [bits[52]:0x7_ffff_ffff_ffff, bits[52]:0x5_5555_5555_5555, bits[52]:0x8, bits[52]:0xa_aaaa_aaaa_aaaa, bits[52]:0xa_aaaa_aaaa_aaaa, bits[52]:0xa_a622_813c_0000, bits[52]:0x1_56f0_78ff_2778, bits[52]:0x7_ffff_ffff_ffff], [bits[52]:0x7_ffff_ffff_ffff, bits[52]:0x6_2a37_d3bc_cff1, bits[52]:0xa_aaaa_aaa0_0400, bits[52]:0x2_0000, bits[52]:0xa_e87a_79cf_aeb8, bits[52]:0x0, bits[52]:0x1_a384_abd3_94f4, bits[52]:0x5_5555_5555_5555], [bits[52]:0x20, bits[52]:0x7_ffff_ffff_ffff, bits[52]:0x7_ffff_ffff_ffff, bits[52]:0x7_ffff_ffff_ffff, bits[52]:0xaa49_ab30_367c, bits[52]:0xa_aaaa_aae3_aaa6, bits[52]:0x7_ffff_ffff_ffff, bits[52]:0xa_aaaa_aaaa_aaaa], [bits[52]:0x10_0000_0000, bits[52]:0xb_c25a_1034_1eeb, bits[52]:0xb_aaaa_aaa0_8000, bits[52]:0xa_aaaa_aa2c_9d4e, bits[52]:0x5_a716_5baa_bee8, bits[52]:0x4_93aa_88aa_dabe, bits[52]:0x0, bits[52]:0xb_e1ae_ef9e_8663], [bits[52]:0x0, bits[52]:0xe_a8aa_aaab_aaea, bits[52]:0x2_403e_7a69_e927, bits[52]:0xa_aaaa_ea8a_aaaa, bits[52]:0x9_640e_de61_0000, bits[52]:0xa_a8aa_fab8_aba8, bits[52]:0x200, bits[52]:0xa_ae2a_aaf9_ffef], [bits[52]:0x7_ffff_ffff_ffff, bits[52]:0xa_2aaa_aa00_8a0a, bits[52]:0xa22a_ebed_3fbc, bits[52]:0x2_edd6_a1e0_3245, bits[52]:0x0, bits[52]:0x200_0000_0000, bits[52]:0xf_ffff_ffff_ffff, bits[52]:0xf_ffff_ffff_ffff], [bits[52]:0xa_aaaa_aaaa_aaaa, bits[52]:0xe_aa9a_b800_0414, bits[52]:0xf_ffff_ffff_ffff, bits[52]:0xa_aea2_aadd_5717, bits[52]:0xa_aaaa_aaaa_aaaa, bits[52]:0xa_aaa2_afd0_f547, bits[52]:0x2000_0000_0000, bits[52]:0x2_0aba_fd84_6079], [bits[52]:0xe_3886_938a_649c, bits[52]:0xa_aaac_aaaf_daf5, bits[52]:0xa_98be_2fbd_af9d, bits[52]:0x1000_0000_0000, bits[52]:0x2_38b9_ba82_9118, bits[52]:0x7_ffff_ffff_ffff, bits[52]:0x5_5555_5555_5555, bits[52]:0x100], [bits[52]:0x2_0fe1_f9ee_b401, bits[52]:0xa_aaaa_aaaa_aaaa, bits[52]:0x8_a60a_ab81_9788, bits[52]:0xb_2aba_aa08_4810, bits[52]:0xa_9bb5_bc8b_bf0b, bits[52]:0x8_aaa9_aaaf_efff, bits[52]:0x10_0000, bits[52]:0xa_aaaa_aaf5_5775], [bits[52]:0xa_aaaa_aad5_5555, bits[52]:0x1_42b4_dce1_0c7f, bits[52]:0x6_73d5_fcce_b35e, bits[52]:0xa_16b9_ef34_0ce3, bits[52]:0x7_ffff_ffff_ffff, bits[52]:0x8_aaaa_aaaa_aaaa, bits[52]:0xf_ffff_ffff_ffff, bits[52]:0xe_e0a0_0a9e_cea4], [bits[52]:0x7_ffff_ffff_ffff, bits[52]:0xe_bfda_a9d6_cdf6, bits[52]:0xf_ffff_ffff_ffff, bits[52]:0x6e0e_bb69_892c, bits[52]:0x8_aaa0_eb97_440c, bits[52]:0x40_0000_0000, bits[52]:0x0, bits[52]:0xf_aafa_bf80_1328]]; bits[8]:0xff'

# This has no value mismatch:
blaze run //xls/tools:eval_ir_main -- --test_llvm_jit --llvm_opt_level=0 --input="$INPUT_ARGS" $MINIMIZED_IR_FILE

# This fails with the value mismatch:
blaze run //xls/tools:eval_ir_main -- --test_llvm_jit --llvm_opt_level=3 --input="$INPUT_ARGS" $MINIMIZED_IR_FILE

[angelomatni1]

Filed LLVM issue llvm/llvm-project#197325 capturing this LLVM opt level 3 vs. opt level 2 bug